Characterization of accessible surface area of HLW glass monoliths by high-energy accelerator tomography and comparison with conventional techniques

Projektdetails

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CSC - Cost-sharing contracts

Ziel

The internal surface of HLW glass blocks is an important parameter of all safety calculations for a final repository because the leaching ratio of radioactive nuclides is proportional to the total accessible surface of the waste loaded glass blocks. In addition the extent of phase separation within glass blocks is important in determining their long-term behaviour in the repository environment. It is proposed to use a technique based on Linac driven computerized tomography to determine these crucial properties of HLW and MLW glass blocks. It is further proposed to compare this technique with existing destructive characterization methods. This proposal builds on work carried out in previous projects under the CEC's programme on RADWAS management and disposal. In contract FI2W-CT90-0023 this technique was demonstrated qualitatively. Quantitative measurements were hampered by the effects of beam hardening on image processing. In contract FI2W-CT91-0107 the use of Cerenkov detectors in CT of radioactive waste was shown to significantly reduce beam hardening. It is proposed to combine the use of Cerenkov detectors, more conventional detectors and theoretical modelling of the system to develop a practical non-destructive technique. Modelling of beam hardening in CT will be carried out by AEA Technology. Measurements with both conventional and Cerenkov detectors will be carried out by BAM. As a result of this work a measurement and image processing procedure will be designed by AEA Technology and BAM, optimised to surface area and phase separation determination. This will be used to measure these properties for specimen blocks supplied by CEA. After measurement the blocks will be returned to CEA, opened and subjected to leach tests for comparison.